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#57060 - 10/04/05 09:58 PM current on GES  
BigB  Offline
Member
Joined: Mar 2004
Posts: 719
Tucson, AZ USA
I just returned from a call where the complaint was intermittent shocks being received from the plumbing. I proceeded to amp out the neutrals and GEC. When the air handler is running there is 7 amps returning from the sub panel to the main neutral bus. However, 2 amps of the 7 leave thru the GEC which is bonded to the water pipe. The other 5 leave thru the main service neutral. I re made all the neutral connections in the panel, meter base and weatherhead. There was no change. My thought is a high resistance connection at the pole mounted transformer, so I called the utility to check.

I ruled out any interior connections as the full 7 amps appears in the sub panels neutral, it does not divide till the main.

Barring a hot wire touching a pipe somewhere, am I on the right track here?


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#57061 - 10/04/05 11:02 PM Re: current on GES  
BobbyHo  Offline
Member
Joined: Jul 2005
Posts: 33
CT
Just a shot,is the house fed by a well?If so is there a water softener? If so check to make sure the outlet for the water softener controls is actually 120 volts from a true 120volt circuit. Water softener companies around my part like to do their own electrical and steal a leg off the 240volt well circuit and use the ground for their neutral. Just a shot but it might be as simple as that.


#57062 - 10/04/05 11:16 PM Re: current on GES  
BigB  Offline
Member
Joined: Mar 2004
Posts: 719
Tucson, AZ USA
No well, no water softener. Gas water heater. It's a very modest 50 + year old home in the city. Occupied by it's original 80 + year old owner.


#57063 - 10/05/05 01:27 AM Re: current on GES  
gfretwell  Offline


Member
Joined: Jul 2004
Posts: 9,099
Estero,Fl,usa
I know the dirt is not supposed to be a current path but there is really no way to stop it. When the ground is wet around here I have a few amps on my GEC too. If I go out to the pole and look at the ground wire coming down to their rod it is carrying a similar current.


Greg Fretwell

#57064 - 10/05/05 07:26 AM Re: current on GES  
resqcapt19  Offline
Member
Joined: Nov 2000
Posts: 2,148
IL
If this buiding is served by a metal underground water pipe system and there are other buildings in the area, it may be normal. Under these conditions the metal underground water pipe is connected in parallel with the grounded conductor per the code rules.
Don


Don(resqcapt19)

#57065 - 10/05/05 01:48 PM Re: current on GES  
winnie  Offline
Member
Joined: Sep 2003
Posts: 649
boston, ma
I'd suggest arranging some down time, and metering for current on the GEC with the main _off_.

I'd also try to narrow down the locations where people are getting shocks from the plumbing, and look for non-bonded metal in those locations.

-Jon


#57066 - 10/05/05 10:39 PM Re: current on GES  
BigB  Offline
Member
Joined: Mar 2004
Posts: 719
Tucson, AZ USA
Don,
I understand how there are parallel paths here, I just thought that 30% of the return current seems high. But if I really think about it, if the water piping system was in great shape electrically, it could conceivably carry half the neutral load! This seems a bit scary to me! But the only reason I can think of why the current would back up into the house plumbing is a bad connection at the service neutral. Sure maybe 2 amps is acceptable at the GEC, but not at the kitchen sink!

Jon, I did pull the meter and the neutral current dropped to zero on all conductors. That is how I verified the current was from the dwelling in question.

Once the POCO re splices I will have to go from there. Maybe I will have to start looking to see if someone lost a neutral and tagged on to a water pipe to fix it. The whole house is two wire, no grounding conductors.


#57067 - 10/08/05 11:53 PM Re: current on GES  
dereckbc  Offline
Member
Joined: Oct 2003
Posts: 156
Tulsa, OK
There are three common items I know of that cause this problem

1. Metalic water pipe between houses/buildings with a common transformer serving them and one house has a high resistance grounded service conductor.

2. A high resistance grounded service conductor, simular to # 1.

3. A very low ground electrode impedance.

First thing I would do is turn off all the breakers and determine if the current is from an outside sources (like comming via water pepe) or generated within. That would give you a good starting point.


#57068 - 10/09/05 07:12 AM Re: current on GES  
iwire  Offline
Moderator
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
BigB I would turn off all the circuits, place the meter on the GEC then turn on each circuit one by one to see if one particular circuit is the culprit or if it is a cumulative problem.

Please post back to let us all know what you found.


Bob Badger
Construction & Maintenance Electrician
Massachusetts

#57069 - 10/09/05 11:25 AM Re: current on GES  
BigB  Offline
Member
Joined: Mar 2004
Posts: 719
Tucson, AZ USA
I did turn everything off, the current disappeared. Current appears whenever any load is turned on at the home, indicating it is from within that home. I am going back next week after the POCO has been there. Maybe like Don said this current is normal, but if the neutral connection was bad wouldn't this cause it to back up into the house plumbing since the water pipes are most likely also high resistance from all the connections/meter etc?


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